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    On the second moment of a stochastic radiation field

    , Article Annals of Nuclear Energy ; Volume 75 , 2015 , Pages 283-291 ; 03064549 (ISSN) Ayyoubzadeh, S. M ; Vosoughi, N ; Ayyoubzadeh, S. M ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    A space dependent model for the second moment of a stochastic field has been presented. The derivation procedure is simple and avoids non-physical assumptions for completeness. Moreover, a program has been developed which obtains the solutions to this equation in the three dimensional space. Two benchmarks, namely the fissile cube and the subcritical slab, show the accuracy of the results obtained using this method  

    Effective moduli and characteristic lengths of micropolar media with dense periodic distribution of ellipsoidal nano-/micro-inhomogeneities

    , Article European Journal of Mechanics, A/Solids ; Volume 85 , 2021 ; 09977538 (ISSN) Alemi, B ; Shodja, H. M ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    Nanoscopic elastic behavior of the field quantities in the vicinities of nanosize defects and nano-inhomogeneities cannot be properly described within the size independent classical theory. As a remedy to this type of dilemmas and enhancement of the accuracy of the solution, polar or gradient continuum theories may be utilized. The current work is concerned with composites consisting of micropolar matrix and micropolar ellipsoidal particles with periodic distribution throughout the three dimensional space. In particular, the analytical determinations of the effective micropolar elastic moduli tensor, effective micropolar couple stress moduli tensor, and effective micropolar characteristic... 

    Effective moduli and characteristic lengths of micropolar media with dense periodic distribution of ellipsoidal nano-/micro-inhomogeneities

    , Article European Journal of Mechanics, A/Solids ; Volume 85 , 2021 ; 09977538 (ISSN) Alemi, B ; Shodja, H. M ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    Nanoscopic elastic behavior of the field quantities in the vicinities of nanosize defects and nano-inhomogeneities cannot be properly described within the size independent classical theory. As a remedy to this type of dilemmas and enhancement of the accuracy of the solution, polar or gradient continuum theories may be utilized. The current work is concerned with composites consisting of micropolar matrix and micropolar ellipsoidal particles with periodic distribution throughout the three dimensional space. In particular, the analytical determinations of the effective micropolar elastic moduli tensor, effective micropolar couple stress moduli tensor, and effective micropolar characteristic... 

    Robustness in fractional proportional-integral-derivative-based closed-loop systems

    , Article IET Control Theory and Applications ; Volume 4, Issue 10 , Volume 4, Issue 10 , 2010 , Pages 1933-1944 ; 17518644 (ISSN) Akbari Moornani, K ; Haeri, M ; Sharif University of Technology
    Abstract
    Robustness of a fractional proportional-integral-derivative (PID)-based control system is investigated. At first the largest pathwise connected region subset of a box in three-dimensional space of the parameters of the model is determined such that the closed-loop system is bounded-input bounded-output stable for any point inside it. Then a value that represents the size (in a specified sense) of the calculated region in the first stage and can be considered as a margin for the robustness of the closed-loop system is computed. Furthermore, lower and upper frequency bounds required in depiction of boundaries of the region and computing the mentioned margin are provided. Some special cases in... 

    Introducing an effective method for extending the high harmonic spectrum plateau from gas targets

    , Article Journal of Physics B: Atomic, Molecular and Optical Physics ; Volume 54, Issue 4 , February , 2021 ; 09534075 (ISSN) Khodabandeh, Z ; Monfared, M ; Majles Ara, M. H ; Sadighi Bonabi, R ; Sharif University of Technology
    IOP Publishing Ltd  2021
    Abstract
    An effective semi-classical method is introduced for controlling the high-order harmonic generation process and extending the cutoff frequency. This method is capable of defining the proper specification of the driving laser for maximizing the cutoff frequency. This method is evaluated by examining the high harmonic spectrum from the hydrogen atom and the fluorine (F2) molecule irradiated by single-, two-, and three-color laser fields. This study is done using the time-dependent density functional theory in a three-dimensional space. The results show that the single-, two-, and three-color laser pulses tuned by proper specifications could extend the cutoff frequency by up to 85%, 176%, and... 

    Behavior of mass concrete using smeared crack approach in three dimensional problems

    , Article 11th International Conference on Fracture 2005, ICF11, Turin, 20 March 2005 through 25 March 2005 ; Volume 3 , 2005 , Pages 1999-2004 ; 9781617820632 (ISBN) Mirzabozorg, H ; Ghaemian, M ; International Congress on Fracture (ICF); European Structural IntegritySociety (ESIS); American Society for Testing and Materials (ASTM) ; Sharif University of Technology
    2005
    Abstract
    A smeared crack approach has been proposed to model the static and dynamic behavior of mass concrete in three-dimensional space. The proposed model simulates the tensile fracture on the mass concrete and contains pre-softening behavior, softening initiation, fracture energy conservation and strain rate effects under dynamic loads. It was found that the proposed model gives excellent results and crack profiles comparing with the available data under static loads. Morrow Point dam was analyzed including dam-reservoir interaction effects to consider its nonlinear seismic behavior. It was found that the resulted crack profiles are in good agreement with the contour of maximum principal stresses... 

    Particle filtering-based low-elevation target tracking with multipath interference over the ocean surface

    , Article IEEE Transactions on Aerospace and Electronic Systems ; Volume 56, Issue 4 , 2020 , Pages 3044-3054 Shi, X ; Taheri, A ; Cecen, T ; Celik, N ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    Abstract
    As radar signals propagate above the ocean surface to determine the trajectory of a target, the signals that are reflected directly from the target arrive at the receiver along with indirect signals reflected from the ocean surface. These unwanted signals must be properly filtered; otherwise, their interference may mislead the signal receiver and significantly degrade the tracking performance of the radar. To this end, we propose a low-elevation target tracking mechanism considering the specular and diffuse reflection effects of multipath propagation over the ocean surface simultaneously. The proposed mechanism consists of a state-space model and a particle filtering algorithm and promises... 

    Development of an equation to predict radial modulus of elasticity for single-walled carbon nanotubes

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 222, Issue 6 , 2008 , Pages 1109-1115 ; 09544062 (ISSN) Sakhaee Pour, A ; Ahmadian, M. T ; Gerami, A ; Sharif University of Technology
    2008
    Abstract
    Finite element (FE) method is used to model radial deformation of single-walled carbon nanotube (SWCNT) under hydrostatic pressure. Elastic deformation of the nanostructure is simulated via elastic beams. Properties of the beam element are calculated by considering the stiffness of the covalent bonds between the carbon atoms in the hexagonal lattice. By applying the beam elements in a three-dimensional space, elastic properties of the SWCNT in transverse direction are obtained. In this regard, influences of diameter and tube wall thickness on the radial and circumferential elastic moduli of zigzag and armchair SWCNTs are considered. It is observed that there is a good agreement between the...